An experimental investigation is proposed to study mass transport in branched tube systems. The objective is to obtain local mass transfer coefficients, particularly in the vicinity of bifurcations, in models which are similar in geometry to the arterial portion of the systemic circulation in mammals. Electrochemical methods will be used to determine limiting mass transfer conditions, using small electrodes mounted flush at locations in the walls of the branched tubes. Various geometries and flow conditions, including both steady and pulsatile flow, will be examined. The data obtained hopefully will be useful in discriminating between conflicting theories on the causative factors involved in atherogenesis and the focal distribution of vascular lesions.